1. Field of the Invention
The invention relates to a capacitive touch panel, and more particularly, to an improvement on the optical characteristic of the sensing structure of the touch panel.
2. Description of the Prior Art
Touch panels are widely used in various consumer electronic products, which allow users to use fingers or touch pen to select desired image or characters from the screen and input information and perform operations by touching the screen of the touch panel.
Touch panels are divided into various types according to different sensing methods, including resistive type, capacitive type, infrared ray type, and ultrasonic type. Infrared ray type and ultrasonic type touch panels preferably dispose an infrared ray or ultrasonic emission source on one side of the X-axis and Y-axis of the screen and set up a receiving source at the other side of the screen. When a user touches the screen, infrared ray or ultrasonic movement is interfered and the coordinates of the interference are measured and determined to complete a touch input. Resistive type touch panels are composed of two indium tin oxide (ITO) conductive films stacked on top of one another, and by applying pressure to electrically connect the two conductive films, a controller is used to measure the voltage difference of the panel and calculate the coordinates of the touch input. Capacitive type touch panels are composed of transparent glass substrates and an oxide metal coated on surface of the glass substrate. The sensing structures of the capacitive type touch panel is composed of two electrode layers electrically connected along an x-axis direction and a y-axis direction, and an insulating layer is disposed between the two electrode layers such that capacitive difference generated from fingers of a user and electrical field is used to determine an touch input.
Referring to FIGS. 1A-1B, FIGS. 1A-1B illustrate a sensing structure 10 of a capacitive touch panel according to the prior art. The sensing structure 10 of the touch panel is typically composed of a substrate 100 and a plurality of sensing units 110 disposed on the substrate 100, in which the sensing units 110 are disposed according to the same or different layer. A portion of the sensing units 110X are electrically connected along a first direction (such as X direction), whereas the other portion of the sensing units 110Y are electrically connected along a second direction (such as Y direction). The sensing units 110X and 110Y are not electrically connected to each other due to the presence of an insulating layer 120 therebetween. A passivation layer 130 is disposed to protect the sensing structure of the touch panel thereafter. By having this type arrangement, a capacitive sensing approach could be established to determine the coordinates touched by the user.
Preferably, the sensing units 110X and 110Y are separated by a distance D. Due to certain limitations from the fabrication process and prevention of electrical interference between sensing units electrically connected from different directions, the sensing units could not be disposed too close to each other and the range of the distance D is therefore restrained. However, the presence of the distance D in most circumstances, allows users to clearly see the array arrangement of the sensing units through the screen (as shown in FIG. 1B) and affects visual perception of the user substantially.
It is therefore a driving motive of the applicant to propose a capacitive touch panel capable of lowering the visibility of the sensing structure therein, and it has also be proven that the proposed structure also has the advantage of easy manufacture and low cost.